Metal Cutting Milling Tools

Abstract

A metal cutting milling tool 100 comprising a body rotatable in a rotational direction about a central axis C, the body comprising a front end 106, a plurality of lands 156 extending axially rearward from the front end 106, and a plurality of chip looms 146 extending axially rearward from the front end, each chip loom 146 of the plurality of chip looms being positioned between two adjacent lands 156 of the plurality of lands, each land 156 of the plurality of lands being bounded in the rotational direction by a front face 157 and a rear face 158, the front face 157 being rotationally forward of the rear face 158, each land 156 as a part of the front face 157 in a radially outer forward region comprising an insert seat 110 for receiving a cutting insert 114, and at the front end 106 of the milling tool 100 in a plane perpendicular to the central axis C, wherein an angle between a radius of the first land (156) intersecting a radially outer point of the insert seat (110) and a radius of the second land (156) intersecting a corresponding point of the insert seat (110) defines a seat pitch angle α of the first land (156), the first and second lands (156) being adjacent consecutive lands in a rotational direction, at least three different lands (156) of the plurality of lands having different values ​​of seat pitch angle α, and at a front end of the milling tool, each land (156) has a respective arc length AL defined by a circumferential distance along the radial circumference of the milling tool (100) between the insert seat (110) and a rear face (158) of the respective land (156), the longest arc length AL being at most 10% longer than the shortest arc length AL.

Description

[Technical Field]

[0001] The present invention relates to metal-cutting milling tools, and more particularly to metal-cutting milling tools with differential pitch for damping vibration during use. [Background technology]

[0002] Vibration, also known as chatter, is a common problem when milling materials such as titanium, steel, aluminum, and castings. Vibration corresponds to relative motion between the workpiece and the milling tool, causing undesirable irregularities / undulations in the machined surface.

[0003] Vibration problems can be solved to some extent by using differential pitch, which means that there is a different angle between two adjacent cutting inserts around the circumference of the milling tool. Having differential pitch allows the engagement frequency of the cutting inserts to be varied, which reduces the risk of self-excited vibration of the milling tool and therefore reduces vibration.

[0004] EP 2335853 discloses a milling tool with differential pitch. The disclosed milling tool incorporates differential pitch by having different angles between cutting inserts along the circumference of the milling tool. The cutting inserts are also positioned at different radial distances from the axis of rotation to achieve a more uniform chip thickness and correspondingly reduce the load on the cutting inserts.

[0005] This known tool works well for most applications. However, in certain applications, the tool may have balance and strength problems that can sometimes result in tool failure.

[0006] Therefore, there is a need for improvements in metal cutting milling tools that alleviate some of the above problems while maintaining the differential pitch of the milling tool. Summary of the Invention

[0007] It is therefore an object of the present invention to provide an improved metal cutting milling tool with differential pitch that alleviates some of the above problems.

[0008] According to the present invention, the above object is achieved by a metal cutting milling tool having the features defined in claim 1.

[0009] The metal cutting milling tool according to the present invention includes a body rotatable in a rotational direction about a central axis, the body including a front end, a plurality of lands extending axially rearward from the front end, and a plurality of chip looms extending axially rearward from the front end. Each chip loom of the plurality of chip looms is positioned between two adjacent lands of the plurality of lands. Each land of the plurality of lands is bounded by a front face and a rear face when viewed in the rotational direction, the front face being rotationally forward of the rear face, and each land includes an insert seat for receiving a cutting insert as a part of the front face in a radially outer forward region. At the front end of the milling tool, in a plane perpendicular to the central axis, an angle between a radius intersecting a radially outer point of the insert seat of a first land and a radius intersecting a corresponding point of the insert seat of a second land defines a seat pitch angle of the first land. The first land and the second land are adjacent, consecutive lands in the rotational direction. At least three different lands of the plurality of lands have different seat pitch angle values. At the leading end of the milling tool, each land has a respective arc length defined by the circumferential distance along the radial periphery of the milling cutter between the insert seat and the trailing surface of the respective land, the longest arc length being up to 10% longer than the shortest arc length.

[0010] The inventors have realized that this configuration alleviates the problem of milling cutter balance and the problem of some lands being significantly weaker than others. Because the arc length of each land differs by up to 10% compared to all other lands, the amount of material behind all insert seats is approximately the same. This material is positioned furthest from the central axis of the milling cutter, which significantly affects cutter balance. Having arc lengths that differ by up to 10% between lands typically implies that it would be difficult to achieve differential pitch to reduce vibration. However, this configuration with different seat pitch angles alleviates this problem, allowing for differential pitch while still having a balanced milling tool where strength between lands is evenly distributed and no lands are significantly weaker than others.

[0011] Having at least three seat pitch angles with different values, i.e., at least three seat pitch angles that are unequal, ensures that the milling tool can reduce vibrations due to differential pitch.

[0012] The term "insert seat" refers more specifically to the bottom of the insert seat, i.e., the surface of the insert seat that contacts the underside of the cutting insert. The underside of the cutting insert is defined as the surface opposite the upper side of the cutting insert, which has a rake surface. The insert seat is not necessarily a single flat surface, but is defined as the area surrounded by the points of the bottom of the insert seat that contact the cutting insert with its flat underside. Thus, the insert seat may be, for example, concave, and only the outer points of the insert seat contact the cutting insert.

[0013] According to one embodiment, the milling tool further comprises cutting inserts positioned one in each of the insert seats, all of the cutting inserts being identical.

[0014] In general, the cutting inserts used may be of any type and do not necessarily have to be identical. However, it is preferred to use cutting inserts that all have the same thickness. It is even more preferred to use cutting inserts that are all identical.

[0015] This configuration implies that all cutting inserts have the same thickness, so that the pitch angle of the cutting insert's cutting edges is the same as the optimum seat pitch angle. This better reduces vibration during use of the milling cutter. Making all inserts identical also greatly simplifies the handling of the inserts when replacing them.

[0016] According to one embodiment, at the front end of the milling tool, in a plane perpendicular to the central axis, a line parallel to the upper side of the cutting insert and a line parallel to the rear side of the adjacent land associated with the same chip room as the cutting insert define opening angles for each cutting insert, where at least three of the opening angles have different values, i.e., at least three of the opening angles are unequal.

[0017] This configuration allows the lengths to have similar arc lengths while providing good vibration reduction during use of the milling tool.

[0018] It is preferable that all the aperture angles have different values.

[0019] This arrangement provides even better vibration reduction during use of the milling tool.

[0020] According to one embodiment, all aperture angles are between 60 and 100°.

[0021] This embodiment only applies to milling tools with up to five cutting inserts.

[0022] With this configuration, the chip room is large enough to allow efficient transfer of chips from the machined surface, while retaining a sufficient amount of material within the milling tool to maintain the strength of the milling tool.

[0023] According to one embodiment, the insert seats each include a threaded hole for fixing one of the cutting inserts, the threaded holes extending across the insert seats. All of the threaded holes are through holes.

[0024] The cutting insert can be secured to the insert seat in a number of ways, including by a clamp or by a fastening element such as a screw inserted into a blind or through hole that passes through the central hole of the cutting insert and extends from the insert seat. Preferably, the cutting insert is secured by a screw inserted into a threaded through hole.

[0025] The advantage of this configuration is that the drilling and threading of the threaded hole can be performed from two directions, simplifying the manufacture of the milling tool. Another advantage is that the threaded hole can be made longer, allowing for the use of longer threads. This improves the stability of the cutting insert in the insert seat.

[0026] Preferably, all of the screw holes extend at the same angle relative to their respective insert seats.

[0027] According to one embodiment, all of the threaded holes extend from one chip loom to an adjacent chip loom in the rotational direction, so that the threaded holes have an opening in one chip loom and an end in the adjacent chip loom.

[0028] According to one embodiment, the longest screw hole is up to 10% longer than the shortest screw hole.

[0029] Preferably, the longest screw hole is at most 5% longer than the shortest screw hole.

[0030] The combination of having the longest threaded hole be up to 10% longer than the shortest threaded hole and having the threaded holes traverse the insert seat implies that all threaded holes end at approximately the same point in their respective arc lengths of their respective chip looms or lands. This simplifies milling tool manufacturing because it is easier to position a manufacturing robot in the correct position for drilling or threading the holes.

[0031] According to one embodiment, the longest arc length is at most 5% longer than the shortest arc length.

[0032] This configuration provides a more balanced milling cutter and provides even more equal strength between the lands.

[0033] According to one embodiment, the shortest arc length is at least as long as the thickness of the cutting insert.

[0034] This configuration ensures that the arc length, and therefore thickness, of the land is sufficient to have a tapped hole and threads of sufficient length to stabilize the cutting insert in the insert seat.

[0035] Even more preferably, the cutting insert has a minimum arc length of at least 1.5 times the thickness of the cutting insert.

[0036] The thickness of the cutting insert is defined as the distance between the top side of the cutting insert and the bottom side of the cutting insert.

[0037] According to one embodiment, the maximum seat pitch angle is at least 5° greater than the minimum seat pitch angle.

[0038] This configuration further enhances the milling tool's tendency to reduce vibrations.

[0039] According to one embodiment, the maximum seat pitch angle is at least 8° greater than the minimum seat pitch angle.

[0040] This configuration further increases the tendency of the milling tool to reduce vibrations.

[0041] According to one embodiment, all seat pitch angles have different values.

[0042] This configuration further enhances the milling cutter's tendency to reduce vibrations.

[0043] According to one embodiment, all cutting inserts are positioned at the same radial distance from the central axis.

[0044] This configuration ensures that all cutting inserts are in operation during milling, regardless of the tooth feed and feed rate used.

[0045] According to one embodiment, the indexable milling tool is an end mill tool.

[0046] This configuration ensures that the milling cutter is suitable for performing square end milling or face milling.

[0047] According to one embodiment, the indexable milling tool is a slot milling tool.

[0048] This configuration ensures that the milling cutter is suitable for slot milling operations.

[0049] Further advantages of the present invention will become apparent from the following description.

[0050] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0051] [Figure 1] FIG. 1 is a side view of a metal-cutting milling tool according to an embodiment of the present invention. [Figure 2]2 is another side view of the metal-cutting milling tool shown in FIG. 1 with a cutting insert attached to the milling tool. [Figure 3] FIG. 3 is an end view of the metal-cutting milling tool shown in FIG. 2 showing the front end of the milling tool. [Figures 4a-4c] FIG. 2 is a cross-sectional view of the metal-cutting milling tool shown in FIG. 1. [Figure 5] FIG. 2 is a cross-sectional view of the metal-cutting milling tool shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0052] The following definitions are valid for all embodiments:

[0053] The seat pitch angle α is defined as the angle between a radius intersecting a radially outer point of the insert seat of the first land portion and a radius intersecting a corresponding point of the insert seat of the second land portion, the first land portion and the second land portion being adjacent consecutive land portions in the rotational direction.

[0054] Arc length AL is defined at the leading end of the milling tool, for each land, as the circumferential distance along the radial periphery of the milling tool between the insert seat and the rear surface of the respective land.

[0055] The pitch angle β is defined at the front end of the milling tool, in a plane perpendicular to the central axis C, as the angle between a line parallel to the top of a first cutting insert and a similar line parallel to the top of a second insert, the second insert being the adjacent consecutive insert in the direction of rotation of the milling tool.

[0056] The opening angle γ of each cutting insert is defined as the angle, at the front end of the milling tool, in a plane perpendicular to the central axis C, between a line parallel to the upper side of the cutting insert and a line parallel to the rear face of the adjacent land associated with the same chip room as the cutting insert.

[0057] Reference will now be made to Figures 1 and 2, which illustrate an embodiment in accordance with the present invention. Illustrated therein is a metal-cutting milling tool, generally designated 100. Metal-cutting milling tool 100 has a rear end 104 for mounting to a rotatable tool holder (not shown), a front end 106, and an outer circumferential surface 108. In this embodiment, outer circumferential surface 108 is generally cylindrical in a region nearest front end 106 and generally conical in a region adjacent the cylindrical region.

[0058] The milling tool defines a central axis C, which is also the longitudinal axis about which the milling tool rotates in a rotational direction R. In the following description, directions described as extending axially are directions substantially parallel to the central axis C, and directions described as extending radially are directions substantially perpendicular to the central axis C.

[0059] The metal cutting tool 100 further includes tangentially spaced chip looms 146 for displacing milled chips from the machining work surface. Disposed between each chip loom 146 are lands 156. The lands 156 function as wings that extend radially from the central axis C. The lands 156 form the radial periphery of the milling tool 100. In the illustrated embodiment, the peripheries of the lands 156 extend axially proximate the leading end 106 and also the trailing end 104, with the peripheries of the lands 156 approaching the central axis C.

[0060] Each land 156 is bounded in the direction of rotation R by a leading surface 157 and a trailing surface 158. The leading surface 157 is rotationally forward of the trailing surface 158. Each leading surface 157 forms a portion of the boundary surface of a corresponding chip room 146 and a portion of the boundary surface of a corresponding land 156. Corresponding here means that features marked with an "a" are associated with other features marked with an "a," features marked with a "b" are associated with other features marked with a "b," etc. Each trailing surface 158 forms a portion of the boundary surface of a chip room 146, trailing surface 158b forms a portion of the boundary surface of chip room 146a, trailing surface 158c forms a portion of the boundary surface of chip room 146b, etc. Furthermore, each trailing surface 158 forms a portion of the boundary surface of a corresponding land 156.

[0061] Each front face 157 has an insert seat 110 for a removably attached cutting insert 114. In this embodiment, all of the cutting inserts 114 are positioned at the front end 106 of the milling tool 100. When the milling tool 100 is used for face milling, each cutting insert 114 has at least one cutting edge extending in the radial direction. When the milling tool 100 is used for square end milling, each cutting insert has at least one cutting edge extending in the radial direction and one cutting edge extending in the axial direction. In this specification, face milling and square end milling are collectively referred to as end milling.

[0062] In this embodiment, the cutting insert 114 is attached by fastening a screw positioned through the threaded hole 112 of the milling tool 100 into the cutting insert's central through-hole. In the illustrated embodiment, each threaded hole 112 extends across the corresponding insert seat 110, and each threaded hole 112 is a through-hole. Each through-hole 112 can be said to originate from the insert seat 110 and terminate either at the radially outer surface of the land 156, at the rear face 158, or partially at the land 156 and partially at the rear face 158. As described in more detail below, all of the threaded holes 112 have approximately equal lengths and terminate at approximately the same location relative to the corresponding cutting insert 114; i.e., the ends of the threaded holes 112 are at approximately the same axial location from the main leading end 106 and at approximately the same tangential distance from the respective insert seat 110 for each threaded hole 112. According to the illustrated embodiment, the longest threaded hole is up to 10% longer than the shortest threaded hole. More preferably, the longest screw hole is up to 5% longer than the shortest screw hole. In the illustrated embodiment, all of the screw holes 112 extend at the same angle relative to their respective insert seats 110. Forming the screw holes 112 as through holes simplifies manufacturing of the milling tool 100 and allows for longer threads, since threading can be performed from both sides of the hole. Having longer threads allows for cutting inserts 114 that are more securely and stably attached to the insert seats 110. The through-hole configuration also simplifies replacing the cutting inserts 114, since the screw can be pushed back if it jams. The advantage of having all of the screw holes 112 be approximately equal in length and end in approximately the same relative position is that manufacturing is greatly simplified. This is because the holes can be drilled and threaded with the same tool for all of the screw holes 112, and if all of the screw holes 112 end in approximately the same relative position, this process is typically performed by an automated robot, making positioning the robot arm easier.

[0063] 3, which is an end view of the milling tool 100 of Figures 1 and 2. The seat pitch angle α is defined as the angle between a radius intersecting a radially outer point of the insert seat 110 of the first land 156 and a radius intersecting a corresponding point of the second land 156, the first land and the second land being adjacent consecutive lands in the direction of rotation.

[0064] At least three of the seat pitch angles α are different, i.e., at least three of the seat pitch angles α are unequal. More preferably, four of the seat pitch angles α are different, and most preferably, all of the seat pitch angles α are different. Preferably, the maximum seat pitch angle α is at least 5° greater than the minimum seat pitch angle. More preferably, the maximum seat pitch angle α is at least 8° greater than the minimum seat pitch angle. This configuration allows for a milling tool 100 with a differential pitch between the cutting inserts 114, i.e., the engagement frequency of the cutting inserts changes as the milling tool rotates and machines the workpiece. This reduces the risk of self-excited vibration in the milling tool 100, thereby reducing vibration. The greater the number of different seat pitch angles α and the greater the difference between the maximum and minimum seat pitch angles, the better the tendency to reduce vibration.

[0065] The arc length AL is defined for each land 156 at the front end 106 of the milling tool 100 as the circumferential distance along the radial circumference of the milling cutter between the insert seat 110 and the rear surface 158 of the respective land 156. The longest arc length AL is at most 10% longer than the shortest arc length AL. Preferably, the longest arc length AL is at most 5% longer than the shortest arc length AL. This configuration improves the balance of the milling tool 100, and the individual lands 156 have more uniform strength compared to known milling tools with differential pitch. The amount of material behind all of the insert seats 110 is more uniform compared to known milling tools with differential pitch. This material is positioned furthest from the central axis C of the milling tool 100, and therefore significantly affects the balance of the milling tool 100. Furthermore, to ensure sufficient strength for all lands 156, the shortest arc length AL is preferably at least as long as the thickness of the cutting insert 114. The thickness of the cutting insert 114 is defined as the distance between the top side of the cutting insert and the bottom side of the cutting insert.

[0066] The pitch angle β is defined as the angle, at the front end of the milling tool, in a plane perpendicular to the central axis C, between a line parallel to the top of the first cutting insert 114 and a similar line parallel to the top of the second insert, the second insert being the adjacent consecutive insert in the direction of rotation of the milling tool 100. By using cutting inserts 114 that are all identical to one another, the pitch angle β is equal to the corresponding seat pitch angle α. This is a significant advantage because the seat pitch angle α is optimized for differential pitch and vibration reduction. Making all cutting inserts 114 identical also simplifies insert handling when changing cutting inserts 114, since there is no risk of mixing up different types of cutting inserts.

[0067] Preferably, all cutting inserts 114 are positioned the same radial distance from the central axis C. The advantage of this is that all cutting inserts 114 are in motion during milling, regardless of the tooth feed and feed rate used.

[0068] The opening angle γ of each cutting insert 114 is defined as the angle, in a plane perpendicular to the central axis C at the front end 106 of the milling tool, between a line parallel to the top side of the cutting insert 114 and a line parallel to the rear face 158 of the adjacent land 156 associated with the same chip room 146 as the cutting insert 114. At least three, and preferably all, of the opening angles γ are different. Furthermore, the opening angles γ range from 60 to 100 degrees. This configuration further enhances the milling tool 100's ability to reduce vibration.

[0069] FIG. 4 is a cross-sectional view of the milling tool 100 shown in FIG. 1. Each chip loom 146 is bounded by a chip loom surface including a rear surface 158 of a first land 156, a front surface 157 of a second land 156, and a bottom surface located between the rear surface 158 and the front surface 157. Here, the first land 156 is rotationally forward of the second land. The minimum radius of curvature r of each chip loom 146 is shown in three different cross sections at various distances from the front end 106 of the milling tool 100. The cross sections are perpendicular to the central axis C. The minimum radius r2 of the second cross section and the minimum radius r3 of the third cross section are larger than the minimum radius r1 of the first cross section. The first cross section is axially forward of the second and third cross sections.

[0070] This configuration alleviates the problem of increasing the strength of a milling tool while having a milling tool with a chip room 146 large enough to accommodate the cutting insert 114. The relatively small radius r1 of the first cross section allows for a deep chip room 146, where the cutting insert 114 is typically positioned, closest to the leading end 106 of the milling tool 100 without removing an excessive amount of material from the milling tool. This is because the relatively small radius r1 narrows the chip room 146. This allows the cutting insert 114 to fit within the chip room 146. Removing a large amount of material from the milling tool 100 would reduce the strength of the milling tool. The relatively large radii r2, r3 of the second and third cross sections allow for a shallower chip room 146 further from the leading end 106 of the milling tool than the first cross section. Having a shallower chip room 146 with a larger radius in this location does not remove as much material from the milling tool in the cross section where strength is most important. Larger radii are also more resistant to crack initiation than smaller radii, so the combination of a relatively small radius r1 on the first cross section and larger radii r2, r3 on the second and third cross sections increases the strength of the milling tool while still having a chip room 146 large enough to accommodate the cutting insert 114.

[0071] The bottom surface of chip loom 146 is the portion of each cross section perpendicular to central axis C where rear surface 158 and front surface 157 meet. The smallest radius of curvature, r, of each chip loom surface in each cross section is found at the bottom surface of chip loom 146. The bottom surface is also preferably the portion of each cross section closest to central axis C of milling tool 100.

[0072] The first cross section is preferably located axially along the axial length of the insert seat 110, and the second and third cross sections are preferably located axially farther from the front end 106 than the axial length of the insert seat 110. The minimum radius r3 of the third cross section is preferably larger than the minimum radius r2 of the second cross section. This preferably results in the radii having a relationship of r3 > r2 > r1. This preferably results in the minimum radii r1, r2, and r3 of the curvature of the chip loom 146 increasing toward the rear end 104 of the milling tool 100. The minimum radius r preferably increases strictly between the minimum radius r2 of the second cross section and the minimum radius r3 of the third cross section. More preferably, the minimum radius r increases linearly between the minimum radius r2 of the second cross section and the minimum radius r3 of the third cross section.

[0073] The axial length of the insert seat 110 refers to the axial distance along which the insert seat 110 has an extension.

[0074] In one embodiment, the minimum radius r1 of the first cross section is substantially constant along the entire axial length of the insert seat 110. The minimum radius r3 of the third cross section is preferably 2 to 10 mm. More preferably, the minimum radius r3 of the third cross section is 2 to 4 times the minimum radius r1 of the first cross section.

[0075] As shown in FIG. 5, the depth of the chip room 146 in the third cross section is less than the depth of the chip room in the first cross section.

[0076] The depth is defined in each cross section as the shortest distance from the bottom of the chip room surface to an imaginary circumferential extension of the outer peripheral surface 108 of the milling tool 100, i.e., the arc obtained when two adjacent land portions 156 are connected by an imaginary arc.

[0077] This configuration ensures that the chip loom does not have unnecessary depth in the cross section away from the front end of the milling tool. The smaller the chip loom depth, the stronger the milling tool.

[0078] The radial distance from the central axis C of the milling tool 100 to the bottom surface is greater in the third cross section compared to the first cross section.

[0079] The bottom surface of the chip room 146 at all cross sections between the second cross section and the third cross section preferably has the shape of a circular arc r4 in a cross section substantially parallel to the longitudinal direction of the chip room 146.

[0080] The length direction of the chip room 146 is the direction of a line passing through the minimum radius r2 of the second cross section and the minimum radius r3 of the third cross section.

[0081] This configuration allows for a smooth transition from a relatively large chip loom 146 near the front end 106 of the milling tool 100 to a relatively small chip loom axially away from the front end of the milling tool 100. This smooth transition minimizes the risk of crack initiation points.

[0082] As shown in FIG. 1, the tip loom 146 preferably extends circumferentially to a point located at the imaginary axial extension of the insert seat 110 .

[0083] The imaginary axially extending portion refers to a portion that occupies the same circumferential position as the insert seat 110 and is axially farther from the front end portion 106 than the insert seat 110 .

[0084] This configuration ensures that there is sufficient chip room space in the immediate axial vicinity of the insert seat 110, and thus, implicitly, also in the axial extension of the cutting insert 114. A sufficiently large chip room 146 is required to effectively displace the chips from the work surface.

[0085] The shape of the chip loom 146 disclosed herein is made possible by freeform ball nose milling.

[0086] The differential pitch invention disclosed in connection with Figures 1-3 can be combined with the invention relating to the shape of the chip room 146 disclosed in connection with Figures 1, 4, and 5 to achieve a milling tool that combines the advantages of these concepts.

[0087] The present invention is shown with five cutting inserts 114 incorporated into the milling tool 100. However, embodiments of the present invention can equally be practiced with milling tools 100 having other numbers of cutting inserts 114, such as, but not limited to, eight, ten, twelve, or twenty cutting inserts 114. The minimum number of cutting inserts 114 is three.

[0088] The present invention is shown incorporated into an end mill tool, however, some of the illustrated embodiments could equally be implemented in a slot milling tool.

Claims

1. A metal cutting milling tool (100) comprising: A body rotatable in a rotational direction around a central axis (C), The body comprises: a front end (106); a plurality of lands (156) extending axially rearward from said forward end (106); a plurality of tip looms (146) extending axially rearward from the forward end; Equipped with each chip loom of the plurality of chip looms (146) is positioned between two adjacent lands of the plurality of lands (156); each of the plurality of land portions (156) is bounded by a front surface (157) and a rear surface (158) when viewed in the rotational direction, and each land portion is configured as a part of the front surface (157) in a radially outer forward region and includes an insert seat (110) for receiving a cutting insert (114); The seat pitch angle (α) of the first land portion is such that, at the front end (106) of the milling tool (100), in a plane perpendicular to the central axis (C): (i) a straight line extending from the central axis (C) through a point on the insert seat (110) of the first land portion that is located radially outward from the central axis (C); (ii) a straight line from the central axis (C) through a point on the insert seat (110) of the second land portion that corresponds to the point and is located radially outward from the central axis (C); and the first land portion and the second land portion are adjacent and consecutive land portions in the rotational direction, At least three different lands of the plurality of lands (156) each have a different value of seat pitch angle (α); at the front end (106) of the milling tool (100), each of the lands (156) has an arc length (AL) defined by the circumferential distance along the radial circumference of the milling tool (100) between the insert seat (110) and the rear surface (158) of the respective land; Of all of the arc lengths (AL), the longest arc length is at most 10% longer than the shortest arc length; the metal-cutting milling tool (100) further comprises cutting inserts (114) positioned one in each of the insert seats (110); at the front end (106) of the milling tool (100), in a plane perpendicular to the central axis (C), a line parallel to an upper side of a cutting insert (114) and a line parallel to the rear surface (158) of the adjacent land associated with the same chip room (146) as the cutting insert (114) define an opening angle (γ) of each cutting insert (114); At least three of the aperture angles (γ) have different values; Metal cutting milling tools.

2. A metal cutting milling tool as described in claim 1, wherein all of the cutting inserts (114) are identical.

3. 2. A metal cutting milling tool according to claim 1, wherein all opening angles (γ) are between 60° and 100°.

4. The insert seats (110) each include a screw hole (112) for fixing one of the cutting inserts (114); 4. The metal cutting milling tool of claim 1, wherein each of the threaded holes (112) extends across the insert seat (110), and all of the threaded holes (112) are through holes.

5. A metal cutting milling tool as described in claim 4, wherein all of the screw holes (112) extend from one chip room (146) to an adjacent chip room (146) in the rotational direction.

6. A metal cutting milling tool as described in claim 4 or 5, wherein the longest threaded hole of all of the threaded holes (112) is up to 10% longer than the shortest threaded hole.

7. A metal cutting milling tool as described in any one of claims 1 to 6, wherein the longest arc length of all of the arc lengths (AL) is up to 5% longer than the shortest arc length.

8. A metal cutting milling tool as described in claim 2 or 3, wherein the shortest arc length of all of the arc lengths (AL) is at least as long as the thickness of the cutting insert (114).

9. A metal cutting milling tool as described in any one of claims 1 to 8, wherein the maximum seat pitch angle (α) of the plurality of land portions (156) is at least 5° greater than the minimum seat pitch angle (α).

10. 10. The metal cutting milling tool of claim 9, wherein the maximum seat pitch angle (α) is at least 8° greater than the minimum seat pitch angle (α).

11. A metal cutting milling tool as described in any one of claims 1 to 10, wherein all of the seat pitch angles (α) of the multiple land portions (156) each have a different value.

12. A metal cutting milling tool as described in claim 1 or 2, wherein all of the cutting inserts (114) are positioned at the same radial distance from the central axis (C).

13. A metal cutting milling tool as described in any one of claims 1 to 12, wherein the metal cutting milling tool (100) is an end mill tool.

14. A metal cutting milling tool as described in any one of claims 1 to 12, wherein the metal cutting milling tool (100) is a groove milling tool.

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